Meta: Port recent changes to the GN build

ccebc7a905e5e358a508dbc580afe9572fffd85d

Meta/gn/secondary/Userland/Libraries/LibWeb/CSS/BUILD.gn

@@ -47,6 +47,7 @@ source_set("CSS") {
     "Resolution.cpp",
     "ResolvedCSSStyleDeclaration.cpp",
     "Screen.cpp",
+    "ScreenOrientation.cpp",
     "Selector.cpp",
     "SelectorEngine.cpp",
     "Serialize.cpp",

Meta/gn/secondary/Userland/Libraries/LibWeb/idl_files.gni

@@ -49,6 +49,7 @@ standard_idl_files = [
   "//Userland/Libraries/LibWeb/CSS/MediaQueryList.idl",
   "//Userland/Libraries/LibWeb/CSS/MediaQueryListEvent.idl",
   "//Userland/Libraries/LibWeb/CSS/Screen.idl",
+  "//Userland/Libraries/LibWeb/CSS/ScreenOrientation.idl",
   "//Userland/Libraries/LibWeb/CSS/StyleSheet.idl",
   "//Userland/Libraries/LibWeb/CSS/StyleSheetList.idl",
   "//Userland/Libraries/LibWeb/CSS/VisualViewport.idl",